insisted that we would anyway. Basically he staked his premiership on this, when it would have been perfectly feasable to say "thanks, George, that gets me out of a right hole. You go ahead and invade and we'll help pick up the pieces afterwards". Why did he do this?

I'd still like to know when the International War Crimes Tribunal on this matter is going to begin, and when the gallows shall be erected! But alas, it seems that only applies when you are the "wrong" side of these wars: